The effect of lattice misfit on the interface structure of γ-Ag2Al precipitates during dissolution

Abstract

Abstract Interfacial dislocation structures present during dissolution of γ-Ag2Al precipitates have been investigated for different precipitate-matrix mismatch values and the results compared to the corresponding structures observed in equilibrated systems. The misfit values were 0.76%, 0.42% and 1.11% for the binary Al-Ag system and with Cu and Mg additions respectively. A stable network of hexagonal (a/6)〈112〉 Shockley partial dislocations was present at the precipitate broadface and edges in all three system during dissolution, in contrast to the non-equilibrium linear array observed in the equilibrated binary and Al-Ag-Cu systems. No structural change occurs in the case of the higher misfit Al-Ag-Mg alloy. Comparison of misfit values obtained from dislocation spacing with those from X-ray diffraction measurement of lattice spacing shows the network structure to be in equilibrium. Evidence detailing the mechanism of transition from the linear to the equilibrium. network structure is presented and discussed. A mechanism of precipitate dissolution involving the network structure is described and compared to the case of precipitate growth.